Frequency alias bug? MS -> millisecond or MonthBegin?

[jseabold]

Likely take me a while to work my way through this again completely. Maybe I'm just misremembering this code, but should MS map to millisecond or month begin? (I was looking for a function to easily and generally say that M, MS, M-Jan, M-Dec, etc. are all monthly frequencies.)

pd.tseries.frequencies.get_standard_freq('MS')
pd.tseries.frequencies.get_freq_group('MS')

vs. things like

pd.tseries.frequencies.get_offset('MS')

and all the rest of the code that gives freq and freqstr MS for month start code like.

pd.tseries.offsets.MonthBegin().freqstr

[cancan101]

See related #5332

[jseabold]

Thanks. I need to start checking existing issues first...

[jtratner]

@cancan101 - okay, you're definitely right this is a problem now that 2
active people have hit it. I'll go back to your fix for this and see
whether we can merge it soon.

[jreback]

closed via #5340